Lecture 3 The Membrane at “Rest”

Well ideal system for biological processes

Info icon This preview shows pages 1–3. Sign up to view the full content.

well → ideal system for biological processes amphiphatic molecules – (usually large macromolecules) containing components with distinctly diff properties nonpolar part – lipid end (fatty molecules)
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

polar region → phosphate group Nonpolar and polar region in one molecule eg phospholipid components of cell membrane; many proteins ; etc many biological building blocks carry charge (amino acids) nonpolar → portion of protein will interact w/non-polar molecules polar/ionized amino acids interact w/aqueous soln non-polar regions can fold upon themselves this gives the macromolecule electrical properties charge is often distributed unevenly Forces acting on ions (2 major) 1. diffusion (not a true force b/c it doesn't have directionality) – the mvmt of molecules down a concentration gradient all molecules in solution are moving (ie have kinetic energy) in a random fashion, thus, tend to go from high concentration to low concentration & vice versa rate of net diffusion is proportional to concentration difference diffusion is very fast but it's time dependent concentration decreases so net flow decreases over time → point to where there is no net flow → doesn't meant that ions have stopped moving. They are moving at same speed and directionality, but it is balanced out from opposite direction. Size of concentration gradient reflects how fast it will tend to move from one side to the other 2. electricity (true force b/c it causes ion to move in a certain directions) – opposite charges attract and like charges repel eg. battery connected to aqueous solution. Anode (+) cathode (-) ions across a membrane – even in the presence of an electrical force, ions cannot pass through membrane unless passages (eg protein channels) are present even there is a force attracting an ion to go in a specific direction, if there are no proteins that allow them to easily move, it won't actually move. Also means that there is a lot of force pulling it, so when the passage actually opens, they will move across rather quickly. electrical chemical equilibrium at electrical chemical equilibrium, electrical force = rate of net diffusion (concentration gradience) forces on a species (type) of ion balance out individual ions still move but there is no net movement (ions are going out at the same
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '08
  • Kippin,T
  • Electric charge, Selective Membrane

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern